HR: 11:30h
AN: PP22A-05 INVITED     [Abstracts]
TI: Radiocarbon variability in the Western-North Atlantic during the last deglaciation
AU: * Robinson, L F
EM: laurar@gps.caltech.edu
AF: Caltech, 1200E California Boulevard, Pasadena, 91125 United States
AU: Adkins, J F
EM: jess@gps.caltech.edu
AF: Caltech, 1200E California Boulevard, Pasadena, 91125 United States
AU: Keigwin, L D
EM: lkeigwin@whoi.edu
AF: Woods Hole Oceanographic Institute, Geology and Geophysics , Woods Hole, MA 02543 United States
AU: Wang, S
EM: jslw@gps.caltech.edu
AF: Caltech, 1200E California Boulevard, Pasadena, 91125 United States
AB: The history of the last deglaciation is complex, and to understand it fully we need to be able to compare different parts of the climate system on a common timescale using tracers that inform us on the rate of changes. High-resolution well-dated records of the deep ocean are difficult to construct because of the problems of bioturbation and variable sedimentation rates. Deep-sea corals are an excellent archive of ocean history since their aragonitic, uranium-rich skeletons are well suited to radiometric U-Th dating. This independent chronometer allows us to calculate the radiocarbon content of the water (D14C) in which the coral grew. Moreover, multiple measurements of 14C within a single coral skeleton create high-resolution D14C-transects of ~100 years. More than 30 samples collected insitu cover the last deglaciation at water depths from 1000-2500m. Comparison with radiocarbon measurements from benthic-planktonic foraminiferal-pairs extends this coverage to the last glacial maximum, and to depths >4500m. We interpret the record in terms of mixing of low and high D14C waters, presumably with a Southern and Northern source respectively. We use the rate of change of D14C to help separate mixing events from insitu decay. The WN Atlantic and atmospheric records exhibit some synchronous changes, for instance reduction of radiocarbon levels at the end of Heinrich 1. The upper part of our record, from 1100-1400m had a constant offset from the atmosphere throughout the deglacial. However, at greater depths (~2000m) we see rapid and large shifts, such as a well defined D14C decrease of >100 per mil at 15.4ka that is not reflected in the atmosphere, or in Northern Hemisphere climate records. Our Atlantic record allows us to investigate the controls on the atmospheric D14C record, namely the interplay between the 14C production rate and its primary sink terms; decay and uptake by the deep ocean.
DE: 1065 Trace elements (3670)
DE: 1635 Oceans (4203)
DE: 4267 Paleoceanography
DE: 4800 OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL
DE: 4860 Radioactivity and radioisotopes
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2005 Joint Assembly